This story is from a book entitled 40 Humourous British traditions available on Amazon:
Turtle Rinsing in London
It’s a little known fact that every turtle that swims up the River Thames past Tower Bridge into the Pool of London
becomes the property and responsibility of the monarch. This rule is part of the Common Law of England and dates back to
the time of Queen Matilda in the 12th Century. The Royal Turtle Surveyor has to be notified if a turtle reaches the Pool of London so the ceremony of Turtle Rinsing can occur. This old procedure involves the Royal Turtle Surveyor, The Royal Turtle Deputy-Surveyor, the Royal Net Bearer, The Royal Water Bagpiper, and the Master of the Hose. From the Tower of London, these five officials proceed towards the turtle in a launch bearing The Royal Standard. Once the turtle is observed by The Royal Turtle Deputy-Surveyor using a spyglass, the Royal Net Bearer apprehends the creature in a special Turtle net that’s over two hundred years old. Once clear of the water, the turtle in the net is raised to shoulder height. Using a 500-year old hose made from Staffordshire Boar hide, the Master of the Hose sprays the creature for “one round of ye reel,” which is danced by the Royal Turtle Surveyor and The Royal Turtle Deputy-Surveyor. The Royal Water Bagpiper accompanies the dance.
Once the reel is complete, the rinsed turtle is returned to the water. In the past, the turtle was observed swimming
vigorously for the open sea; however in recent years they have mainly hung around HMS Belfast waiting for tourists to
drop food to them. Historians believe that the Turtle Rinsing was created because of Matilda’s desire to keep her supporters happy by giving them jobs in the Royal Household that were purely ceremonial in nature. Other such jobs include The Royal Wasp Counter in the Hunting Forests, The Royal Cloud Shape Describer, and the Royal Maker of Cubes from Honey.